With the application of precision hirth couplings indexing table in precison mechanical machining field,the needs for large load capacity is proposed. Based on the analysis of the structure of the hirth-coupling indexing table, the FEA and design and experiments are carried out on the parameters of hirth sharp, locking force and meshing state of the hirth. A new kind of gear lapping process is proposed, which improves the precision and efficiency of the hirth lapping, and finally guarantees the precision of the high load hirth couplings indexing table.